__all__ = ['Composer', 'ComposerError']
from error import MarkedYAMLError
from events import *
from nodes import *

class ComposerError(MarkedYAMLError):


class Composer(object):

    def __init__(self):
        self.anchors = {}



    def check_node(self):
        if self.check_event(StreamStartEvent):
            self.get_event()
        return (not self.check_event(StreamEndEvent))



    def get_node(self):
        if not self.check_event(StreamEndEvent):
            return self.compose_document()



    def get_single_node(self):
        self.get_event()
        document = None
        if not self.check_event(StreamEndEvent):
            document = self.compose_document()
        if not self.check_event(StreamEndEvent):
            event = self.get_event()
            raise ComposerError('expected a single document in the stream', document.start_mark, 'but found another document', event.start_mark)
        self.get_event()
        return document



    def compose_document(self):
        self.get_event()
        node = self.compose_node(None, None)
        self.get_event()
        self.anchors = {}
        return node



    def compose_node(self, parent, index):
        if self.check_event(AliasEvent):
            event = self.get_event()
            anchor = event.anchor
            if (anchor not in self.anchors):
                raise ComposerError(None, None, ('found undefined alias %r' % anchor.encode('utf-8')), event.start_mark)
            return self.anchors[anchor]
        else:
            event = self.peek_event()
            anchor = event.anchor
            if (anchor is not None):
                if (anchor in self.anchors):
                    raise ComposerError(('found duplicate anchor %r; first occurence' % anchor.encode('utf-8')), self.anchors[anchor].start_mark, 'second occurence', event.start_mark)
            self.descend_resolver(parent, index)
            if self.check_event(ScalarEvent):
                node = self.compose_scalar_node(anchor)
            elif self.check_event(SequenceStartEvent):
                node = self.compose_sequence_node(anchor)
            elif self.check_event(MappingStartEvent):
                node = self.compose_mapping_node(anchor)
            self.ascend_resolver()
            return node



    def compose_scalar_node(self, anchor):
        event = self.get_event()
        tag = event.tag
        if ((tag is None) or (tag == u'!')):
            tag = self.resolve(ScalarNode, event.value, event.implicit)
        node = ScalarNode(tag, event.value, event.start_mark, event.end_mark, style=event.style)
        if (anchor is not None):
            self.anchors[anchor] = node
        return node



    def compose_sequence_node(self, anchor):
        start_event = self.get_event()
        tag = start_event.tag
        if ((tag is None) or (tag == u'!')):
            tag = self.resolve(SequenceNode, None, start_event.implicit)
        node = SequenceNode(tag, [], start_event.start_mark, None, flow_style=start_event.flow_style)
        if (anchor is not None):
            self.anchors[anchor] = node
        index = 0
        while not self.check_event(SequenceEndEvent):
            node.value.append(self.compose_node(node, index))
            index += 1

        end_event = self.get_event()
        node.end_mark = end_event.end_mark
        return node



    def compose_mapping_node(self, anchor):
        start_event = self.get_event()
        tag = start_event.tag
        if ((tag is None) or (tag == u'!')):
            tag = self.resolve(MappingNode, None, start_event.implicit)
        node = MappingNode(tag, [], start_event.start_mark, None, flow_style=start_event.flow_style)
        if (anchor is not None):
            self.anchors[anchor] = node
        while not self.check_event(MappingEndEvent):
            item_key = self.compose_node(node, None)
            item_value = self.compose_node(node, item_key)
            node.value.append((item_key, item_value))

        end_event = self.get_event()
        node.end_mark = end_event.end_mark
        return node




